It is known from New Zealand patent specification 233,083 that synthetic combinations of endophyte/herbage cultivars can be made which are resistant to pests and can be less toxic to grazing animals than naturally occurring combinations. The desired properties were achieved by selecting synthetic combinations which produced relatively high levels of peramine and relatively low levels of or no lolitrem B in ryegrass.
It has been found that the ergopeptine alkaloid, ergovaline, was produced in a synthetic endophyte/perennial tall fescue combination and that livestock grazing on the combination had an adverse physiological reaction to ergovaline under specific conditions.
Naturally occurring endophytes in populations of tall fescue cultivars in the United States of America (for example, Kentucky 31 tall fescue) generally have high levels of toxicity in the warm seasons. We have screened many such combinations but have been unable to locate any which produce levels of ergovaline sufficiently low to be candidate selections for making acceptable synthetic endophyte/tall fescue combinations. We have been able to find a few strains from Mediterranean locations which are able to meet the primary selection criteria of effective absence of ergovaline and a satisfactory level of peramine, an insect resistance factor.
It is an object of this invention to go some way towards avoiding the above mentioned disadvantages and achieving the aforementioned desiderata or at least to offer the public a useful choice.